Fluorescence resonance energy transfer (FRET) enables photosynthetic light harvesting¹, wavelength downconversion in light-emitting diodes² (LEDs), and optical biosensing schemes³. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells⁴, non-contact chromophore pumping from a proximal LED⁵, and markedly reduced gain thresholds⁶. However, the fastest reported FRET time constants involving spherical quantum dots (0.12–1 ns; refs 7, 8, 9) do not outpace biexciton Auger recombination (0.01–0.1 ns; ref. 10), which impedes multiexciton-driven applications including electrically pumped lasers¹¹ and carrier-multiplication-enhanced photovoltaics^12, 13. Few-monolayer-thick semiconductor nanoplatelets (NPLs) with tens-of-nanometre lateral dimensions¹⁴ exhibit intense optical transitions¹⁴ and hundreds-of-picosecond Auger recombination^15, 16, but heretofore lack FRET characterizations. We examine binary ​CdSe NPL solids and show that interplate FRET (∼6–23 ps, presumably for co-facial arrangements) can occur 15–50 times faster than Auger recombination^15, 16 and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies.

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4231.html

Nature Materials (2015) doi:10.1038/nmat4231